Alkylation of paraffin hydrocarbons



Dec' 30 1941 A. v. GRossE ETAL ALKYLATION OF PARAFFIN HYDROCARBONS Filed Dec. 31, 1938 fPatented Dec. 30, 1941 ALKYLATICN F PARAFFIN HYDRO- CABBO Aristid V. Grosse and Carl B. Linn, Chicago, Ill., assignors to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application December 31, 1938, Serial No. 248,777

17 Claims.

This invention is more particularly concerned with the interaction of isomeric or branched chain paraiiin hydrocarbons andy mono-olefinic hydrocarbons in the presence of catalysts. It is more specifically concerned with a simple and easily regulated process involving the use of a liquid catalyst which is only slightly altered in the course of the reactions and which catalyzes the desired reactions with a maximum of eiiiciency.

Processes for the formation of higher molecular weight branched chain hydrocarbons from essentially straight chain compounds or less highly branched compounds are of present importance from the standpoint of the motor fuel industry which demands increasing quantities of isoparaflins within the boiling range of gasoline and particularly iso-octanes, such as, for example, the 2,2,4-trimethyl pentane which forms the standard of reference in rating the antiknock value of gasolines. Considerable quantities of butanes and butenes are available as by-products from the cracking of petroleum fractions to produce relatively high primary yields of gasoline and by proper segregation oi butanes and butenes by solvent extraction and fractionation methods, particular cuts are available for recombination to produce material yields of the desired iso-octanes. Efforts to alkylate normal butae with butenes in the presence of catalysts have thus far failed unless concurrent isomerization of the normal butanes to iso-butane occurs. However, iso-butane fractions may be made to interact with butenes and particularly isobutene in the presence of various catalysts to form variable iso-octanes.

Catalysts previously tried to effect the alkylation of iso-paramn hydrocarbons with olefin hydrocarbons include sulfuric acid, phosphoric acid, aluminum chloride, and boron fluoride, all of which have disadvantages which are in a large measure overcome by the use of the catalysts of the present invention. Sulfuric acid, for example, can not be used to effect alkylation with ethylene and gives very poor yields when propylene is used. Furthermore, this acid has a tendency to oxidize hydrocarbonswith the formation of sulfur dioxide so that the catalyst is gradually lost by reduction and the products of the reactions are contaminated with sulfur compounds and oxidation products.

Phosphoric acid has a limited application but the reactions are not accelerated to a practical degree unless undesirably high temperatures are employed. Aluminum chloride and similar mulparaiiln hydrocarbons with mono-oleiinic hydrocarbons in the presence of liquid hydrogen fluoride under controlled conditions of operation.

We have determined thatl whereas previous work in alkylating various classes of hydrocarbons with oleflns has indicated that the reactions could be brought about in the presence of boron fluoride and minor amounts of hydrogen iiuoride, the reactions are better brought about when using merely liquid anhydrous hydrogen fluoride. This catalyst is a liquid boiling at about 20 C. so that it can be used in apparatus which is cooled to maintain temperatures below this point or can be used at higher temperatures if suicient pressures are maintained upon the apparatus. By maintaining an excess of iso-paraflin at all times, polymerization reactions and the formation of alkyl fluorides are minimized so that the products consist principally of alkylated derivatives of the original iso-paraiins. The catalystl is not changed byoxidation or reduction and if lost mechanically it can be readily recovered and reused while any alkyl fiuorides formed are readily decomposable.

In operating the present process, the preferred procedure is to agitate a mixture of liquid hydrogen fluoride and an iso-paraffin and gradually introduce a mixture of an olefin and an iso-paraffin below the surface of the hydrogen fiuoride-isoparafiin mixture. In the batch operation of this process, the agitation may be stopped and the upper hydrocarbon layer fractionated to recover unchanged parailins and the desired alkylated products. Obviously the process may be made continuous by providing a mixing zone in which suiiicient time is given for the completion of the desired reaction followed by a settling zone from which a hydrocarbon layer is withdrawn and fractionated to recover desired alkylated products and paraiiin for rev cycling, while the lower hydrogen fluoride layer is pumped back for further service.

The present process includes the alternative of using hydrogen fluoride generated in situ by the interaction of strong mineral acids such as sulfuric acid with fluorides although it will be obvious to those skilled in these types of operations that the preferred procedures outlined for batch and continuous operations respectively will need to be modified somewhat.

For' the purpose of illustrating a characteristic apparatus hook-up in which the processlmay be conducted, the attached drawing shows diagrammatically in general side elevation and by the use of conventional figures an arrangement of interconnected units suitable for continuous operations. It is understoo'd that minor features of apparatus construction may be modified without departing essentially from the generally broad scope of the invention- Referring to the drawing, liquid iso-paraffin hydrocarbons may be introduced through line I containing valve 2 to line 3 containing valve 4 leading to pump 5 While liquid hydrogen fluoride is introduced to line 3 by Way of line 6 containing valve 1. Pump 5 discharges through 'line 8 containing valve 9, line 8 receiving a regulated andcontinuous'stream of olens, or olens plus iso-paraiiins, from line I containing valve II, the mixture passing through line I2 containing valve I3 and through a cooler I4 of any suitable construction and capacity for maintaining the temperature of reaction below any desired level While at the same time permitting time for the` completion of the reactions. The reaction products'follow line I5 containing valve I6 to a receiver I1 in which a separation of hydrogen fluoride and hydrocarbons is effected. The hydrogen fluoride is withdrawn from `the receiver through a line I8 containing Valve I9 and returned by pump 20 which discharges through line 2| containing -valve 22 into line 23 leading to the suction side of pump so that the hydrogen fluoride catalyst is completely recycled.

The hydrocarbon layer in the upper portion of receiver I1 passes through line 24 and valve 25 and enters fractionation column 26 containing a reboiler 21, unconverted low boiling hydrocarbons being removed as overhead while higher boiling alkylated products of the reaction are withdrawn through line 28 containing valve 29 from the bottom of the column.

'I'he overhead products pass through line 30 containing valve 3| through condenser 32 and thence through rundownline 33 containing a valve 34 to receiver 35 which has a conventional gas release line 36 containing valve 31 and a liquid draw line 38 containing valve 39 leading to a pump 40 which discharges through line 4I containing valve 42 to storage if desired, but ordinarily through line 43 containing valve 44 and leading to line 23 to permit the further alkylation of the paraflins.

The exact temperatures and pressures which should be employed when alkylating various isoparaflins with various olefins will depend upon the activity and physical characteristics of the hydrocarbons involved so that best results will be obtained when conditions are first determined in small scale apparatus. As a rule, excessive elevated temperatures are not necessaryA or` desirable and onlysuj'cient pressures should be used to prevent excessive evaporation of lthe 'catalyst or the hydrocarbons.

For the recovery for reuse of hydrogen iiuoride which may combine with oleiins toform alkyl fluorides in the course of the alkylating reactions, these uorides may be passed over granular iluorides such as calcium fluoride or aluminum uorides which decomposes them into hydrogen fluoride and the corresponding olens. The mixture of olefin and hydrogen fluoride is then passed over solid granular sodium or potassium fluorideg which forms addition compounds of the type NaF.HF. The olefin liberated may be recycled for further use and the hydrogen fluoride recovered from the double salt by heating.

The following experimental data is given by way of example to indicate the results obtainable when utilizing the present process for alkylating iso-butane with butenes to form isooctanes. This example has been chosen because of its commercial importance and it is not to be inferred that the scope of the invention is limited in exact correspondence with the data presented.

Concentration of hydrogen fiuoride To determine whether the anhydrous material and the Water solutions of hydrogen fluoride could be usedv interchangeably or with substantially equivalent effects, tests were conducted using 100% anhydrous material, a 90% aqueous solution, and a '15% aqueous solution. An approximately molal requivalent mixture of iso-,butane and iso-butene was passed into the acids of varying concentration at temperatures from 20-30 C., the runs being made in a continuously stirred pressure autoclave. Using 100% anhydrous hydrogen fluoride, the recovered hydrocarbon layer consisted of 60% octanes of which about half was 2,2,4-tri-methyl pentane. lThe hydrocarbon layer was completely saturated and contained only 0.1% of uorine. With the 90% aqueous solution and amolal ratio of parailin to olefin of 1.5:1, the hydrocarbon layer consisted of 48% octanes and there was present 1% of uorine. With a 75% acid solution, an equivalent molal ratio'of paraffin to olefin and a temperature of 12 C., no alkylation occurred, lbut there was considerable formation of butyl fluorides, iso-butenes forming tertiary butyl fluoride vand normal butenes forming secondary butyl fluorides.

Efect of temperature Using a mixture of iso-butane and iso-butenev fluoride, best results were obtained at room temperature. At temperatures within the range of -50 to 60 C., no alkylation occurred, but there was considerable polymerization of iso-butene. The hydrocarbon layer contained 2% fiuorine. At a temperature of C. utilizing suiiicient pressure to maintain liquid phase and with a paraflin-olen ratio of 1:3, the hydrocarbon products consisted of only 20% octanes and a large amount of more highly alkylated derivatives. Temperatures as high as C. may be used, if desired, by suitable adiustment of time factor, olefin-paraflin ratio, and amount of catalyst used.

Effect of paran-olefn ratio Using a molal ratio of parafrin'to olefin of 3:1, temperatures from 20-30 C. and 100% hydrogen fluoride, 65% of hydrocarbon product boiling within the octane range and 50% of this material was 2,2,4-tri-methyl-pentane. The percentage of fluorine in the total hydrocarbon products was 0.1%. Using a paraii'in-olefin ratio of 1:3 and the same temperature and other operating conditions, 50% of the hydrocarbon products boiled above 200 C. and contained 5-10% olefin polymers indicating that over-alkylation and polymerization had both taken place.

E'ect of contact time This factor was found to vary with the temperature employed and the reactivity of various iso-paraflins and olefins which may be brought` together.

We claim as our invention:

1. A. process for synthesizing hydrocarbons which comprises reacting an iso-paraffin with an olen under alkylating conditions and in the presence of an alkylating catalyst consisting essentially of hydrogen fluoride as its active ingredient.

2. A process for synthesizing` hydrocarbons which comprises reacting an iso-paraflinwith an olefin under alkylating conditions and in the presence of an alkylating catalyst consisting essentially of anhydrous hydrogen fluoride.

3. A process for synthesizing hydrocarbons which comprises reacting an iso-paraffinwith an olefin under alkylating conditions and in the presence of an alkylating catalyst consisting essentially of liquid anhydrous hydrogen fluoride.

4. A process for producing iso-octane which comprises reacting iso-butane with a butene under alkylating conditions and inthe presence of an alkylating catalyst consisting essentially of hydrogen iiuoride as its active ingredient.

5. The process as defined in claim 4 further characterized in that the hydrogen fluoride is anhydrous.

6. A process for producing iso-octane which comprises reacting iso-butane with a butene in the presence of an alkylating catalyst consisting essentially of anhydrous hydrogen iiuoride and under temperature and pressure conditions such as to maintain the hydrogen iiuoride in liquid phase.

'7. A process for synthesizing hydrocarbons which comprises subjecting a mixture of an isoparailin and an olefin, containing a molal excess of the former, to alkylating conditions in the `presence of an alkylating catalyst consisting es'- sentially of hydrogen fluoride as its active in-` gredient.

8. A process for producing iso-octane which comprises subjecting a mixture of iso-butane and a butene, containing a molal excess of the former, to "alkylating conditions in the presence of an alkylating catalyst consisting essentially ofv hydrogen fluoride as its active ingredient.

9. A process which comprises contacting a low boiling isoparaiiin with a mono-olefin in the presence of a composition containing anhydrous hydrogen fluoride as the sole catalytic alkylation component under superatmospheric pressure and suitable alkylating conditions for a sufficient period of time to produce saturated normally liquid hydrocarbons.

l0. A process for synthesizing hydrocarbons which comprises reacting an isoparaiiin with an olefin under alkylating conditions and in the presence of an alkylating catalyst consisting essentially of hydrogen fluoride.

11. An alkylation process whichtcomprises intimately mixing iso-paraffinic and olelinic hydrocarbons with a liquid alkylating catalyst consisting essentially of hydrogen uoride as its active ingredient, subjecting the mixture to alkylating conditions while maintaining a suflicient excess of iso-paraffin over olen to effect alkylation of iso-paraffin with olefin as the principal reaction in the process with minimum olefin polymerization, and separating resultant alkylation products from the catalyst.

12. The process as defined in claim 11 further characterized in that the iso-paraffinic hydrocarbons comprise iso-butane.

13. A process for` producing iso-octane which comprises intimately mixing isobutane and a butene with a liquid alkylating catalyst consisting essentially of hydrogen fluoride as its active ingradient, subjecting the mixture to alkylating conditions while maintaining asuiiicient excess of isobutane over butene to effect alkylation of isobutane with butene as the principal reaction in the process,V and thereafter recovering isooctane from the reaction mixture.

14. A continuous alkylation process which comprises reacting isobutane with an olefin in a reaction zone maintained under alkylating conditions and While in admixture with an alkylating catalyst consisting essentially of hydrogen iiuoride as its active ingredient, removing from said zone a reaction mixture of hydrocarbons and catalyst and separating the mixture into a hydrocarbon layer and a hydrogen fluoride layer, fractionating the hydrocarbon layer to Separate alkylated hydrocarbons from unreacted isobutane; and returning at least a portion of said unreacted isobutane and at least a portion of said hydrogen iiuoride layer to the reaction zone.

15. The process as defined in claim 14 further characterized in that said olefin is a butene.

16. An alkylation process which comprises reacting an iso-paraflin with an olefin in the presence of an alkylating catalyst containing at least of hydrogen fluoride as its essential alkylating component, while maintaining alkylating 

